The present invention relates to a method for positioning the ends of fibres in a fibre optic array.
Image projection systems are known in which it is desired to project a television image onto one side of a screen of, for example, spherical shape. In such systems it may be advantageous to produce a line scan which is transmitted down a fibre optic ribbon to a projection lens and a frame scanner in the form of an oscillating mirror, or else to project in some other way the image produced in a fibre optic array.
If it is desired that the projected image subtends a large angle such as 90.degree. from the projection point, then the projection lens can conveniently be spherically symmetric with the output end of the fibre optic array arranged in a predetermined orientation relative to the lens. The optic fibres making up the array must be very accurately positioned so as to be radially directed relative to the centre of spherical symmetry.
It is known to manufacture a fibre optic ribbon by winding an optic fibre around a drum, applying a strip of adhesive across the width of the winding to maintain the relative positions of individual turns of the winding, cutting through the fibres and the strip of adhesive across the width of the winding so that the severed ends of the fibre are secured by the adhesive on both sides of the cut, and then unwrapping the resultant ribbon from the drum.
The above method provides a coherent fibre optic ribbon, there being a one to one correspondence between fibres at each end, but a ribbon unsuited for wide angle projection unless the individual fibres at the cut ends are then re-positioned and re-directed appropriate to such projection. Such positioning, as taught in the present invention, allows a further exploitation of whatever projection lens or mirror is used. For example, conventional lenses have symmetry about one single axis and will best image the light from any given fibre only when that fibre is orientated appropriately for its position. In this case, though each fibre-image will be optimised, image quality will be unequal. In contrast, in for example the case of lenses with optical symmetry about a point, the fibres can be positioned so that performance is simultaneously both optimum and equal for every fibre across the entire field of view.